Shaykh Saalih Al Fawzaan said:

Indeed, giving from the goodness of wealth and halal earnings for the sake of Allah is from the most exalted forms of worship. As worship can be by way of actions of the limbs, similarly it can also be by way of wealth. For this reason Allah, the exalted, has placed zakah as a pillar of Islam, which is giving a known portion of your wealth to those who are needy and underprivileged. 
So Allah placed zakah which is a type of giving in charity from the pillars of Islam.
So it is upon a Muslim to know this and to fulfil what Allah has made obligatory upon him regarding the known right (of the poor) from his wealth. And that he gives in charity voluntarily from that which he has as a surplus and that he should not deprive himself of its reward, especially during this blessed month (of Ramadhan) and the seasons of goodness.
A person should not look down upon giving in charity if it is the case that it is little (i.e. If what he is able to give is little, he should not be discouraged and refrain from giving it). For indeed Allah, the exalted, saves a person from the Hellfire by their giving of half of a date in charity.

The Prophet (sallaaAllahu alayhi wa sallam) said: “Protect yourself from the Hellfire even if it is by giving half of a date in charity, for whosoever cannot find it, then by saying a good word“. [Al-Bukhari # 1413, 3595 and Muslim #1017]
Allah accepts the giving in charity from his believing slave and multiplies its reward for him until it may become like an enormous mountain. Therefore let not a person despise anything that he can give as charity from his wealth even if it is little, so what about if he can give a lot? (i.e. If the reward of a small charity can be multiplied so greatly by Allah, then think about what one could earn by giving more or a lot).
With good wealth (given in charity) Masjids are able to be built, also schools, spreading of good and striving in Allah’s cause. So therefore that wealth could be spent in so many things, its opportunities of spending is vast and the good that it brings for those who spend it in Allah’s obedience is numerous.

Allah says: {The likeness of those who spend their wealth in the Way of Allah, is as the likeness of a grain (of corn); it grows seven ears, and each ear has a hundred grains. Allah gives manifold increase to whom He pleases. And Allah is All-Sufficient for His creatures’ needs, All-Knower}. [Al-Baqarah verse: 261]

Therefore a person must not allow the love of (keeping) wealth overcome (and control) him and also being scared of his wealth decreasing or being stingy, and that he should not deprive himself from (spending and earning the rewards of) his wealth for indeed your wealth is a loan in your hands and Allah may give you an opportunity to spend a portion of it in charity and to spend it on yourself. So if a person prevents himself from giving charity and he just accumulates it, then indeed eventually he will depart from this world and he will leave it behind and its benefit will be left for others whilst the fatigue of acquiring and counting it was upon him. So why would a person deprive himself of it? Why did he acquire and gather this wealth? And he knows that he will soon be departing (from this world) and that he would not benefit from this wealth except that which he puts forth for himself (as reward) before his death or after his death as an ongoing charity which benefits him (with reward) after his death.
The Prophet (sallaaAllahu alayhi wa sallam) said: “When the son of Adam dies, his actions are cut off except for three: an ongoing charity or knowledge which is benefited from or a righteous child who supplicates for him”. [Muslim #1631]

Then a Muslim should know that Allah the Exalted is good and he does not accept anything except that which is good. So a person should not spend in charity from haram wealth and repugnant earnings. For indeed, Allah does not accept these.
Likewise, (it is better that) a person should not give in charity from the worst of his wealth which is small in benefit.
Allah says: {O you who believe! Spend of the good things which you have (legally) earned, and of that which We have produced from the earth for you, and do not aim at that which is bad (radee) to spend from it, (though) you would not accept it save if you close your eyes and tolerate therein. And know that Allah is Rich (Free of all wants), and Worthy of all praise}. [Al-Baqarah verse: 267]

The meaning of bad (radee) here in this verse is not that which is Haram, but that in the case where a person does not want his food which is unpleasant so he goes and gives it as charity. And Allah has prohibited this: {and do not aim at that which is bad (radee) to spend from it} (verse above). Therefore a person should not (aim) to give in charity only his thobes that he finds torn or ripped and cannot be worn or can only be used for a short time. Likewise, for food, he should not give in charity only that which he does not desire. This is not true (giving in) charity, it is instead merely getting rid of things (that are unwanted). And this (with this intention) does not benefit a person before Allah, the Exalted.
Allah says: {By no means shall you attain Al-Birr (piety, righteousness, it means here Allah’s Reward, i.e. Paradise), unless you spend (in Allah’s Cause) of that which you love; and whatever of good you spend, Allah knows it well}. [Aali Imran verse: 92]
And Allah says: {And they give food, inspite of their love for it (or for the love of Him), to Miskin (poor), the orphan, and the captive} [Al-Insaan verse: 8]
They give food which they want and love for their own selves, but they give precedence to Allah’s love over the love for their own selves. {By no means shall you attain Al-Birr (piety, righteousness, etc., it means here Allah’s Reward, i.e. Paradise), unless you spend (in Allah’s Cause) of that which you love; and whatever of good you spend, Allah knows it well}. [verse above]

This is what is befitting for a person to spend from, which are things that are beneficial, especially if he loves it himself. He gives it in charity whilst he loves it himself. This is a sign of his eemaan and a sign of him giving precedence to Allah’s pleasure (over himself). As Allah, the Exalted, says about the Ansaar: {And (they) give them (emigrants) preference over themselves, even though they were in need of that. And whosoever is saved from his own covetousness, such are they who will be the successful}. [Al-Hashr verse: 9]
We ask Allah to guide all to that which he loves and is pleased with. May Allah’s mention be upon our Prophet Muhammad.

Partly summarised 

Majaalis Shahr Ramadhan 21-24